GLACIERS OF PASSAGE CANAL AND BLACKSTONE BAY
and 1880 an advance of from one to three miles, by the forward movement and union of the two side glaciers, thus filling the pass with a double-ended through glacier.
Stagnation in Recent Years. We have no evidence of changes in Portage Glacier between 1880 and 1887, nor between 1887 and 1898. From 1898 to 1909, when the eastern end of the glacier was mapped and briefly described by Grant and Higgins, there was little change (Fig. 51), and between 1909 and 1910 there was no noticeable change. In the latter year, the glacier surface had little morainic debris and there were no conspicuous moraines. As seems to have been the case throughout its recent history, the ice at the time of our visit was only moderately crevassed. We observed no barren zone around the glacier borders, and mature trees on parts of the outwash
Submerged contour -nterva, ZOO feet
FIG. 54. MAP SHOWING INNBB POBTION OF PASSAGE CANAL (POSTAGE BAT) WITH SOUNDINGS MADE IN 1910.
Soundings in feet. Submerged contour interval, 200 feet. (Outline of coast and glaciers after Grant and Higgins.)
gravel plain, between the glacier and the head of Passage Canal, show that it could not have reached tidewater at any time in its recent history.
Learnard Glacier. Learnard Glacier,1 a smaller ice tongue north of Portage Glacier, terminates within a quarter of a mile of the fiord (Fig. 54), to which it sends a stream over the outwash gravel plain in front of Portage Glacier. The glacier slopes with a very low grade and ends in the mouth of a deep, narrow valley. It is considerably encumbered with morainic debris, so that its terminus is dark.
Detached Ice Mass. . Between the terminus of the glacier and the head of the fiord is a large, irregular-shaped hill, which from a distance looks like a mine dump, but -which is really a detached mass of ice covered over with angular ablation moraine, including much black slate. This debris has retarded melting during the period since
1 Named in 1910 for Lieut. H. G. Learnard.